1. Field
This case relates to drill bit systems for drilling geological formations, and more particularly to drill bit systems incorporating temperature sensors. This case also relates to the use of temperature sensor measurements obtained from drill bits having temperature sensors, including, but not limited to the use of the measurements to improve drill bit reliability, to predict wear, and to increase drilling efficiency.
2. Background
Geological formations are drilled for exploration and exploitation purposes. In commercial environments, the drilling may include a drilling rig and a drill string with a drill bit located at the distal end of the drill string. Different types of drill bits are known, including roller cone bits and polycrystalline diamond compact (PDC) bits. Roller cone bits include a plurality of cutting elements arranged on two or three cones that rotate on bearings about their own axis as the drill string turns the body of the bit. PDC bits include a plurality of fixed (also called “stationary”) lands or blades separated by flutes with the blades including a plurality of synthetic diamond discs (teeth) that provide a scraping cutting surface as the drill string turns the body of the bit. While PDC bits rotate about the longitudinal axis of the drill string, they are often called “stationary” bits because they do not also rotate separately as do roller cone bits.
PDC bits drill primarily due to a wedging mechanism that involves scraping and grinding. More particularly, a vertical force is applied to the teeth as a result of applying drill collar weight to the bit, and a horizontal force is applied to the teeth as a result of applying torque that turns the bit. The result of these forces defines the plane of thrust of the teeth. As the forces are applied, the teeth shear off cuttings from the formation. As the PDC bit encounters the formation, the PDC bit heats up due to friction. In order to reduce the heat build-up, it is common to inject a drilling “mud” through the drill string and down to the bit to cool the bit. Thus, in drilling into the formation, the drill operator may control the drill string RPM, the mud flow-rate, and the weight-on-bit (WOB), each of which will impact the build-up of heat at the drill bit.
Drill bit failure requires a tripping of the drill string out of the borehole, and tripping is costly because of the time and effort involved. Drill bit failure can occur for various reasons including gradual bit wear, bit damage (e.g., loss of one or more cutter elements), and bit balling (i.e., accumulation of clay or other materials coating the bit face and preventing the cutter elements from gaining purchase into the formation).